Modelling responses to nutritional, endocrine and genetic strategies to increase fertility in the UK dairy herd

The United Kingdom, as in most countries using intensive dairy management programmes, is facing serious challenges in terms of dairy cow fertility, as highlighted by a rapidly increasing calving interval (CI). A mechanistic, mathematical model is described that predicts the size of the future national dairy herd required to supply domestic requirements and its inherent sustainability in terms of production of replacement female numbers. The results from the model suggest that continuing use of current management strategies may result in the national dairy herd being unsustainable due to increasing CI and reduced fertility in as few as 10 years. Adoption of nutritional, endocrine and genetic techniques that increase fertility can effectively and rapidly reverse this trend and reduce the required size of the national herd, thereby reducing methane emissions from dairy production.     

Teladorsagia circumcincta egg output at the onset of natural and induced lactation in ewes

Nineteen ewes maintained under 'worm-free' conditions received anthelmintic and 1 week later were dosed on 5 days each week with 500 Teladorsagia circumcincta larvae for between 10 and 12.5 weeks. Faecal egg counts were determined twice weekly. There were three groups: pregnant (P) ewes (n = 6) which each reared twin lambs, hormone-treated (H) ewes (n = 7) which were not pregnant and were given exogenous hormones (dexamethasone, oestradiol-17 beta, progesterone) for 37 days to induce udder development and milk production, and untreated barren (B) ewes (n = 6). The plasma concentrations of oestradiol-17 beta, prolactin and progesterone were measured. Starting 10-15 days before birth in Group P, there was a biphasic periparturient rise in egg count and the onset of the first peak in egg count preceded the parturient peak in plasma prolactin concentration by several days. Most Group H (5/7) and all Group B ewes remained highly resistant to Teladorsagia infection throughout, despite an induced rise in prolactin concentrations in Group H ewes. It was concluded that factors other than prolactin initiate the periparturient rise but that prolactin is one factor which maintains the response once lactation commences.     

直接饲喂微生物在有机家禽生产中的应用及存在问题

<正>随着全球饲料需求量的增加,畜牧业巨大的压力来自在提高动物生产力的同时,还要保证畜禽产品的质量和安全。营养补充剂和抗生素在畜牧业的应用已取得了长足发展。尽管抗生素在提     

Inhibitors of biotin biosynthesis as potential herbicides: part 2

Isosteres and analogues of 7-keto-8-aminopelargonic acid (KAPA) and 7,8-diaminopelargonic acid (DAPA), the vitamer intermediates involved in the biosynthetic pathway of biotin, possessing chain lengths of eight carbon atoms, were prepared and evaluated as potential herbicides. The most active compounds, 7-amino-octanoic acid hydrochloride and 7-allyloxy-6-oxo-octanoic acid, displayed Arabidopsis GR50 (concentration of the active compound that causes a 50% growth inhibition) values of 5 and 10 mg kg(-1) respectively. The DAPA analog 6,7-diamino-octanoic acid dihydrochloride, when tested in the greenhouse against six weed species, displayed moderate activity against three species, being most active against foxtail millet.     

Strategies for reversing the trend towards subfertility in dairy cattle

The calving rate of the modern dairy cow is declining at approximately 1% per annum. First service conception rates are now below 40%, and the average cow requires more than two inseminations to get her in calf. We review here genetic, endocrine and nutritional strategies for reducing subfertility, and we emphasize the role of milk progesterone data in the analysis of the condition. Milk progesterone data underpin three approaches to treating subfertility; firstly, they allow the identification of specific reproductive abnormalities which can be treated pharmacologically. Secondly, they show that at least one endocrinopathy is heritable, thereby providing the basis for a selective breeding strategy. Thirdly, they provide a means for monitoring ovarian (and indirectly uterine and conceptus) function during early pregnancy, which are central to the successful establishment of pregnancy, and are amenable to dietary modification. These approaches to reversing the falling fertility of dairy cows are characterized by different timescales.     

Ecosystem UV-B experiments in terrestrial communities: a review of recent findings and methodologies

Ecosystem-level UV-B experiments have revealed a variety of responses in terrestrial communities. These include decreases in the growth of some plant species (usually small changes but occasionally >25%), both decreases and increases in herbivory, occasional altered decomposition patterns, changes in populations of fungi and invertebrates, and morphological changes in the growth patterns of mosses. These field experiments have been pursued both with solar UV-B exclusion using selective filters and with supplementation of UV-B using lamps. For UV-B-exclusion studies it is critical that the UV-B-excluding and UV-B-transmitting filters pass the same amount of photosynthetically active radiation (PAR, 400–700 nm) and also infrared. Canopy photosynthesis models indicate that even small differences in PAR transmittance can, under many circumstances, have significant effects on plant carbon gain. It is also important that filters in UV-B-exclusion studies allow precipitation to pass uniformly to the plots unless there is some form of irrigation underneath the filters. For UV-B-supplementation studies with lamps, many factors are involved in the realism of the ozone depletion simulation. We believe the major lamp-system error is excessive supplementation of UV-B by timer-controlled lamps when weather conditions (primarily clouds) decrease ambient solar UV-B irradiance. The choice of biological spectral weighting functions (BSWF) used in adjusting lamp flux is also critical in determining the level of ozone depletion simulated. In addition, shading by the lamp arrays influences plant growth and becomes particularly important when BSWF with substantial weighting in the UV-A are employed.     

Status of the Pleistocene Wisconsin Stage in Central North America

A brief review of the history of the Wisconsin Stage in Pleistocene stratigraphy and of research since 1950 shows that post-Sangoman glacial drift older than the Wisconsin drift reported in the older literature is present in central North America. Known and possible stratigraphic positions of the relevant units are shown.     

Climate and land change impacts on future managed wetland habitat: a case study from California’s Central Valley

Landscape Ecology - California’s Central Valley provides critical habitat for migratory waterbirds, yet only 10% of naturally occurring wetlands remain. Competition for limited water supplies...